Is the backlight actually all that much of a differentiator? It seems like it should be, but apart from the greater uniformity of a backlight, what are the practical differences? This question of emissive versus reflective light is itself a fuzzy distinction because, with an LCD, you're seeing light bounced through the diffuser behind the liquid crystal, not directly from the CCFL or LED.

There is, however, a surprisingly major difference (at least to me) which is highlighted by this microscope comparison: Dot pitch. The iPad's IPS panel has a pretty average dot pitch, but I was surprised to see that the Kindle's e-ink display has essentially none. Even though the eye compensates for dot pitch, I have to wonder if that still might make a difference.